首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2801篇
  免费   146篇
  国内免费   31篇
耳鼻咽喉   69篇
儿科学   88篇
妇产科学   72篇
基础医学   450篇
口腔科学   42篇
临床医学   228篇
内科学   671篇
皮肤病学   74篇
神经病学   186篇
特种医学   81篇
外科学   418篇
综合类   13篇
预防医学   137篇
眼科学   48篇
药学   139篇
中国医学   1篇
肿瘤学   261篇
  2023年   33篇
  2022年   44篇
  2021年   90篇
  2020年   50篇
  2019年   58篇
  2018年   87篇
  2017年   63篇
  2016年   71篇
  2015年   90篇
  2014年   105篇
  2013年   138篇
  2012年   192篇
  2011年   209篇
  2010年   125篇
  2009年   97篇
  2008年   170篇
  2007年   169篇
  2006年   169篇
  2005年   189篇
  2004年   179篇
  2003年   143篇
  2002年   127篇
  2001年   33篇
  2000年   35篇
  1999年   24篇
  1998年   29篇
  1997年   22篇
  1996年   26篇
  1995年   15篇
  1994年   13篇
  1993年   9篇
  1992年   23篇
  1991年   13篇
  1990年   11篇
  1989年   22篇
  1988年   11篇
  1987年   10篇
  1986年   10篇
  1985年   12篇
  1984年   3篇
  1983年   8篇
  1981年   4篇
  1980年   5篇
  1979年   5篇
  1976年   8篇
  1975年   3篇
  1968年   3篇
  1966年   2篇
  1964年   2篇
  1963年   2篇
排序方式: 共有2978条查询结果,搜索用时 125 毫秒
91.
92.
This study hypothesized that the well-being of community residents in remission from major depression disorder (MDD) would not be significantly different from those without MDD. Data from the Midlife in the United States Survey (MIDUS), a prospective general population survey conducted in 1995 and 2004, were analysed. A comparison of the psychological well-being scores, Big Five personality scores and life satisfaction scores of remitted and non-remitted respondents revealed generally small effect size differences. The remitted group were more likely than the non-remitted group to have had past-year panic disorder at follow-up. In general, these results suggest that the well-being of respondents in MDD remission was relatively high.  相似文献   
93.
We investigated the signal transmission pathway by which activation of μ-opioid receptors attenuates acetylcholine (ACh) release in bovine trachealis. Electrical stimulation (ES)-induced [3H]-ACh release was determined in bovine tracheal smooth muscle strips pre-incubated with either the Gi-protein inhibitor pertussis toxin (PTX, 500 ng/ml and 1 μg/ml) or the Gz-protein specific inhibitor arachidonic acid (AA, 10−6 M and 10−5 M) and then treated with DAMGO (D-Ala2,N-MePhe4,Gly-ol5-enkephalin) 10−5 M. Indomethacin 10−5 M was used to block AA cascade. The inhibitory effect of DAMGO on ES-induced [3H]-ACh release was PTX-insensitive, but, by contrast, ablated by AA in a concentration-dependent manner. AA 10−5 M alone reduced [3H]-ACh release, an effect that was prevented by iberiotoxin 10−7 M, suggesting an involvement of Ca2+-activated K+-channels. Western blot analysis consistently showed immunoreactive bands against a specific antibody anti-Gz-α subunit at ∼40 kDa, consistent with the presence of Gz-protein. The present findings suggest that in isolated bovine trachealis, activation of μ-opioid receptors inhibits ACh-release through a signal transmission pathway involving Gz-protein rather than Gi-protein.  相似文献   
94.
A subset of over-expressed microRNAs (miRNAs) identified in parathyroid carcinomas (Ca) compared to normal glands belongs to C19MC, a cluster on chromosome 19q13.4 involved in stem cell biology and tumourigenesis. In this study, the expression of C19MC-MIR371-3 clusters and the molecular mechanisms presiding their modulation were investigated in a series of six normal parathyroids, 24 adenomas (Ad), 15 Ca and five matched metastases. The general expression levels of C19MC or MIR371-3 clusters in Ad lesions did not differ from normal glands, while they distinguished Ad from Ca at unsupervised hierarchical cluster analysis (P=0.0008). MIR517C showed the most significant difference in expression between Ca and Ad (P=0.0003) and it positively correlated with serum calcium, parathormone and tumour weight. In regard to the molecular mechanism determining C19MC cluster activation, we could detect C19MC copy number (CN) gain in ten Ca (67%) extending distal to the MIR371-3 cluster in almost all samples. Conversely, only four Ad (16%) showed C19MC amplification, with one case presenting distal genomic aberration to MIR371-3. Globally, CN variations of 19q13.4 loci were significantly associated with MIR517C up-regulation (P=0.006). Opposite to normal glands where C19MC promoter was methylated, hypomethylation occurred in 15 out of 30 analysed tumours. Though the epigenetic status did not correlate with C19MC miRNA expression levels, loss of C19MC promoter methylation was significantly associated with Ca and metastatic disease (P=0.01). In conclusion, C19MC cluster aberrations are a characteristic of Ca with respect to Ad. Altogether, these evidences point towards a role for 19q13.4 miRNA clusters as oncogenes in parathyroid tumourigenesis.  相似文献   
95.
BackgroundThere is no gold standard for the differential diagnosis of acute dyspnea despite the usefulness of N-terminal pro–B-type natriuretic peptide (NT-proBNP) and lung ultrasound. No study has evaluated the contribution of bioelectrical impedance vector analysis (BIVA) in discriminating between cardiac and noncardiac dyspnea. We sought to determine whether a relationship exists between ultrasound detection of lung congestion, NT-proBNP, and BIVA in patients with acute dyspnea.Methods and ResultsEligible patients were between 50 and 95 years, with an estimated glomerular filtration rate of ≥30 mL min?1 1.73 m?2, who presented to an emergency department with dyspnea. Dyspnea was classified by reviewers blinded to BIVA as cardiac or noncardiac based on physical examination, electrocardiogram, chest X-ray, NT-proBNP, and B-lines of lung congestion on ultrasound. Overall, 315 patients were enrolled (median age 77 years, 48% male). An adjudicated diagnosis of cardiac dyspnea was established in 169 (54%). Using BIVA, vector positions below ?1 SD of the Z-score of reactance were associated with peripheral congestion (χ2 = 115; P < .001). BIVA measures were reasonably accurate in discriminating cardiac and noncardiac dyspnea (69% sensitivity, 79% specificity, 80% area under the receiver operating characteristic curve).ConclusionsIn patients presenting with acute dyspnea, the combination of BIVA and lung ultrasound may provide a rapid noninvasive method to determine the cause of dyspnea.  相似文献   
96.
97.
98.
BackgroundAtrophic gastritis of the corporal mucosa is a frequent cause of hypergastrinemia. Hypergastrinemia is implicated in colorectal cancer development.AimTo assess whether hypergastrinemic atrophic gastritis is associated with a higher risk of neoplastic colorectal lesions.MethodsAmong 441 hypergastrinemic atrophic gastritis patients, 160 who were aged >40 and underwent colonoscopy for anaemia, diarrhoea or colorectal cancer-screening were retrospectively selected. Each patient was age- and gender-matched with a normogastrinemic control with healthy stomach. Controls had colonoscopy, gastroscopy with biopsies and gastrin assessment.Results160 hypergastrinemic atrophic gastritis patients and 160 controls were included. 28 atrophic gastritis patients and 36 controls had neoplastic colorectal lesions (p = 0.33). Patients and controls did not differ for frequency of colorectal adenomas (10.6% vs. 13.1%, p = 0.60) or cancer (6.9% vs. 9.4%, p = 0.54). Hypergastrinemic atrophic gastritis was not associated with a higher probability of developing colorectal cancer (OR 1.03, 95% CI 0.34–3.16). Age >50 years (OR 3.86) but not hypergastrinemia (OR 0.61) was associated with colorectal cancer.ConclusionsHypergastrinemic atrophic gastritis is not associated with higher risk for colorectal cancer. Atrophic gastritis-related hypergastrinemia is not associated with an increased risk of neoplastic colorectal lesions. Closer surveillance of colonic neoplasia in atrophic gastritis patients seems not appropriate.  相似文献   
99.

Background

Intestinal anastomosis is a complex procedure during laparoscopy, mainly due to the difficulties knotting the sutures. Unidirectional barbed sutures have been proposed to simplify wall and mesentery closure, but the results for intestinal anastomosis are not clear. This study aimed to establish the feasibility and the safety of laparoscopic intestinal anastomosis using barbed suture.

Methods

Between June 2011 and May 2012, 15-cm-long unidirectional absorbable barbed sutures (V-Loc; Covidien, Mansfield, MA, USA) were used for all laparoscopic intestinal anastomoses: one suture for closure of intestinal openings after mechanical anastomoses and two sutures for hand-sewn anastomoses.

Results

Over a 1-year period, 201 consecutive patients required 220 laparoscopic anastomoses for gastrojejunostomy (n = 177; 172 during Roux-en-Y gastric bypass and 5 after gastrectomy), ileocolostomy (n = 15), colocolostomy (n = 1), esophagojejunostomy (n = 5), and jejunojejunostomy (n = 22; 4 after small bowel resection and 18 during gastric bypass or gastrectomy). Senior and training surgeons performed 209 closures of intestinal openings and 11 hand-sewn anastomoses. There was no conversion to usual sutures. One fistula occurred in an esophagojejunostomy and was managed conservatively. One self-limited anastomotic bleeding occurred, and no anastomotic stenosis occurred during 6 months of follow-up evaluation.

Conclusions

The use of knotless barbed suture for laparoscopic intestinal anastomosis is safe and reproducible.  相似文献   
100.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号